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We present a neutron scattering study carried out on single-crystals of the magnetoelectric compound GaFeO3, prepared by the floating-zone (FZ) method. The refinement of the crystal structure indicates the existence of a large amount of iron on the gallium site, corresponding to a strong internal substitution disorder. We show that the Ga/Fe disorder and the magnetic transition temperature are weakly dependent on the growth conditions. The disorder also affects the magnetic excitations; our measurements evidence damped spin waves, well defined only close to the Brillouin zone centre.

Polycrystalline two-layered perovskite La2.5-xK0.5+xMn2O 7 + δ (0 < x < 0.5) samples have been prepared by a modified sol-gel method and their magnetoresistance and magnetocaloric effects have been studied. A large deviation between the metal-insulator (MI) transition temperature (T ρ ) and the magnetic transition temperature (TC) is observed. Large magnetoresistance (MR) effects with Δρ/ρ of ∼40% at 12 kOe are obtained in wide temperature ranges. The maximum of the magnetic entropy change peaks at its Curie temperature (TC), far above its MI transition temperature (T ρ ). The large magnetic entropy change (∼1.4 J/kg.K) is obtained in the sample La2.5-xK0.5+xMn2O 7 + δ (x = 0.35) upon 10 kOe applied magnetic field.

The temperature dependence of the electric quadrupole interaction and the magnetic hyperfine field at 111Cd probe sites in RMn2 (R=Gd, Tb) has been studied by TDPAC method. In the paramagnetic region the quadrupole interaction frequency νQ in both compounds varies linearly with temperature. Below the Neel temperature, we find an abrupt decrease in the magnitude of νQ which is consistent with an expansion of the unit cell. As an important feature, the data near TN shows the coexistence of localized and itinerant magnetism of Mn atoms.

The random bound mixed compound Fe(Br0.8I0.2)2has been investigated by magnetization and Mossbauer spectroscopy. The experimental results for Fe(Br0.8I0.2)2were compared with those of Fe(Br0.6I0.4)2studied previously. A magnetic structure below the magnetic transition temperature observed by Mossbauer spectroscopy has been suggested which shows a large distribution ofthe hyperfinefields.

The goal of this research is to prepare a series of alloys having sharp, reproducible magnetic transitions for calibrating temperature in thermogravimetry from the magnetic transition temperature of pure cobalt (1121°C) to below room temperature. Alloys in the Ni-Co and Ni-Cu systems were prepared by the thermal decomposition of coprecipitated oxalates in argon. The alloys were subsequently annealed under 5% hydrogen. Magnetic transition temperatures were measured using simultaneous thermomagnetometry/differential thermal analysis. Transition temperatures were corrected using well known meltingpoint standards. Magnetic transition temperatures along with precision are reported as a function of composition.

Magnetic properties of TlBa2Y1-xCaxCu2Oy which is one of the hole‐doped high‐TC superconducting (SC) oxides were investigated by zero‐field μ+SR. Two precession frequencies of the muon spin were observed for x=0, indicating the existence of a coherent long range antiferromagnetic ordered state of Cu‐spins. The saturated internal fields at the muon sites, Hint, was 170 Oe and 23 Oe, respectively and magnetic transition temperature, TN, was about 400 K. Both Hint and TN show no x‐dependence up to x=0.5. No sign of the magnetic ordered state was observed in the SC state for x=1.0 down to 1.8 K.

Hole doped high-Tc oxide of TlBa2Y1−xCaxCu2Oy, Tl-1212, has been investigated by μ+ SR technique from an insulating to a superconducting (SC) region. Fast and slow precession components of the muon spin asymmetry which are due to an antiferromagnetic (AF) ordering of Ce-spins were observed from x=0 to x=0.5. The magnetic transition temperature (about 400 K) and local μ+ fields were found to have no x-dependence. No sign of the magnetic transition was observed for x=1.0 down to 1.8 K. The correlation between the AF ordered state and the SC state at the boundary of the two states (x=0.6) was examined.

In the last decade we have obtained a deeper understanding of basic magnetism in alloys and a variety of new magnetic materials have been developed. In this review article two kinds of recent topics in these fields will be discussed. The first one is the magnetic properties of rare earth-3d transition intermetallics. After describing the magnetic properties of RMn2 very briefly, we discuss the magnetic properties of YMn2 in detail, particularly its magnetovolume effect which is closely related with the magnetic moment of Mn atoms below and above the magnetic transition temperature. Then, as an example of recent developments in soft magnetic materials, Fe-Ni-Cr alloys with very high permeability and low coercive force will be discussed including impurity effects on their magnetic properties.

THE magnetic property of the ultrafine particles differs from that ot the bulk materials and has a lot of applications. Because of the size effect, magnetically ordered materials exhibit both superparamagnetism and collective magnetic excitation, and the magnetic transition temperature changes in the ultrafine particles with respect to the bulk materials as well. Bulk α-Fe2O3 is weakly ferromagnetic above the Morin transition temperature TM(263......

Temperature and dopant concentration dependence of magnetic properties of TIBa2Y1−xCaxCu2Oy were investigated by μ+SR at RIKEN-RAL Muon Facility. Fast and slow coherent precession of the muon spin were observed up tox=0.5, proving the existence of a long range antiferromagnetic ordered state of Cu-spins. The magnetic transition temperature was about 400 K and showedx-independence up tox=0.5.

Heat capacity and magnetisation measurements are reported on polycrystalline samples of Pd2Gd x La1−x In. For x=1, a Curie-Weiss susceptibility is indicated down to approximately 15K with a magnetically ordered state at temperatures below 9K. Anomalies are seen in specific heat measurements with the magnetic transition temperature and magnetic entropy decreasing with decreasing x. Subtraction of the lattice and electronic contributions to specific heat for the x=1 compound indicates a magnetic entropy of Rln(7.87) in good agreement with theory. Above magnetic ordering temperatures the specific heat remains high with an enhanced electronic heat capacity coefficient. γ=(250+/−20) mJ mol−1 K−2 for x=1.

This paper reports on optical, magnetic, and specific heat experiments at low temperatures on DyVO4 and DyAsO4, including a summary of previous works on these two substances. The crystallographic phase transition in DyVO4 is second order, whereas in DyAsO4 there is a latent heat at the distortion temperature. In contrast to the results of neutron diffraction experiments, no evidence for a canted antiferromagnetic structure in DyAsO4 below the magnetic transition temperature was found. Magnetically, DyAsO4 behaves almost identically to DyVO4.

A description of itinerant ferromagnetism is presented, which allows for a local exchange splitting without long range order. The five-fold degeneracy of thed-bands is contained in the model, the parameters of which may be determined from first principles by fitting a given bandstructure. The theory is applied to derive the magnetic transition temperature. Numerical results are presented forT c of Iron and Nickel in good agreement with experiment. The occurence of antiferromagnetism in Mn and Cr can also be understood in the framework of the theory presented here.

F-riebeckite has been subjected to analysis by 57-Fe Moessbauer spectroscopy from 4. 2K to 501K. The spectra obtained above the magnetic transition temperature, were analyzed in terms of three ferrous doublets in M1, M3 and M2 sites and two ferric doublets occupying M2 and M1 sites. The ratios of these occupations, together with their quadrupole splittings, were then used to fit the 4.2K magnetic spectrum.

The first observation of a new class of icosahedral phase associated with a magnetic transition in Fe-Cu and Fe-Mo systems are reported. It is found that the icosahedral order can be re-established when the destabilized Fe60Cu40 icosahedral phase subject to a magnetic transition at high annealing temperature. The Fe70Mo30 amorphous films obtained by sputtering exhibit a similar behavior at high magnetic transition temperature. A brief discussion of the observed phenomena is addressed.

The hydrogen rich ternary hydride phases of RFe2Hx (R=Y Dy, Er) with x>4 have been investigated using 57Fe, 161Dy and 166Er Mössbauer spectroscopy and bulk magnetization. In all cases, the presence of hydrogen results in a dramatic reduction in the moment on Fe as well as the magnetic transition temperature. The data also imply a simultaneous weakening of the R-Fe magnetic exchange.

COBALT ferrite (CoO.Fe2O3) and magnetite (FeO.Fe2O3) both crystallize at room temperature with the inversed-spinel-type of structure1. A magnetic transition consisting of an abrupt decrease of saturation magnetization takes place in magnetite2 at 116° K., and is accompanied by a slight deformation of the structure cell from cubic symmetry above the transition to approximately rhombohedral symmetry below3. As cobalt ferrite4 undergoes a similar magnetic transition at 90° K., we might expect that, like magnetite, it is no longer cubic below its magnetic transition temperature. We have shown by means of X-ray powder photography that this is indeed true, but the departure from cubic symmetry is even smaller than in the case of magnetite. Our results indicate that the structure cell of cobalt ferrite at low temperatures is approximately tetragonal.